Devel::Leak has two functions NoteSV and CheckSV.

NoteSV walks the perl internal table of allocated SVs (scalar values) -
(which actually contains arrays and hashes too), and records their
addresses in a table.  It returns a count of these "things", and stores
a pointer to the table (which is obtained from the heap using malloc())
in its argument.

CheckSV is passed argument which holds a pointer to a table created by
NoteSV.  It re-walks the perl-internals and calls sv_dump() for any
"things" which did not exist when NoteSV was called.  It returns a count
of the number of "things" now allocated.